1. Technical Field
The present invention relates to a resistor-sharing switching circuit.
2. Description of the Related Art
FIG. 1 is circuit diagram of a general radio frequency (RE) switching circuit.
Referring to FIG. 1, a switching device is provided between a transmission end and an antenna and between a reception end and the antenna to alternately connect the transmission end or the reception end to the antenna according to a control signal. Here, by applying a control signal of 0 V or −3 V to a body of the switching device, objectives such as removing low-frequency noise may be achieved.
Meanwhile, while a signal transmitted from the transmission end to the antenna and/or a signal transmitted from the antenna to the reception end has relatively great power, a breakdown voltage of the switching device such as a transistor which is typically used in an RF switching circuit is relatively low, and thus a plurality of transistors that are serially connected are used between the transmission end and/or the reception end and the antenna. When a plurality of serially connected transistors are used, the number of resistors connected to a control terminal of each of the transistors is also increased.
In addition, when generally forming an RF switching circuit using a chip, space occupied by a transistor constituting the switching device and a resistor connected to a body terminal of the transistor in the chip, in which the RF switching circuit is implemented, is very large. For example, in the case of a single-pole-double-through (SPDT) RF switching circuit, an area occupied by a resistor connected to a body terminal of a switching device is about 8% of the entire chip area.
Since the compact size and light weight of electronic appliances become important issues, efforts have been made to reduce a chip size, but it is difficult to manufacture compact chips as long as the number of transistors and the number of resistors connected to a body of the transistor in an RF switching circuit are not reduced.